Improve `ethereum-spec-new-fork` to support blob parameter only hardforks

[SamWilsn]

With the introduction of EIP-7892, we need to support Blob Parameter Only (BPO) hardforks.

Although they are similar to the glacier forks in that they only tune constants (and make no other changes), unlike glacier forks they are going to get more thorough testing.

I'd like to rewrite ethereum-spec-new-fork so that it:

1. Is more robust;
2. Requires no human-tuning after running;
3. Supports setting FORK_CRITERIA; and
4. Supports changing BPO parameters.

The end goal is to have t8n use the tool to generate a sequence of forks based on a BPO schedule.